sonares

Sonares are underwater acoustic detection and ranging systems used to detect objects, map underwater environments, and aid navigation. The term sonar derives from Sound Navigation and Ranging and is widely used to describe both active systems, which emit acoustic pulses and listen for echoes, and passive systems, which listen for sounds produced by other objects.

Active sonares transmit pulses, and the time between emission and received echo yields range. The frequency, pulse length, and beamwidth determine resolution and detection depth. Transducers convert electrical energy to sound; hydrophone arrays receive echoes and, through signal processing and beamforming, estimate direction and, with Doppler, relative speed.

Passive sonares rely on hydrophone arrays to detect sounds produced by ships, animals, or geological processes. Without emitting signals, they determine bearing and sometimes speed by acoustic triangulation.

Common configurations include hull-mounted, towed-arrays, variable-depth sonar, and side-scan or synthetic-aperture sonares, each optimized for range, resolution, or seabed mapping. Advances in digital processing have expanded versatility and imaging capabilities across platforms.

Applications span military anti-submarine warfare, navigation and mine avoidance, underwater mapping, fisheries, and archaeology. In civilian contexts, sonar aids harbor safety, offshore construction, and scientific study of the marine environment.

Limitations include sound-speed variability with depth and water properties, environmental noise, absorption, and interference from marine life. Acoustic systems also raise considerations about environmental impact and regulatory restrictions on noise in sensitive areas.

See also: Echo sounding, hydrophone, multibeam sonar, side-scan sonar, towed array, synthetic-aperture sonar.